Rheological and curing behavior of reactive blending. I. Maleated natural rubber-cassava starch

Maleated natural rubber (MNR) was prepared and used as a blending compositi on and a compatibilizer for blending of natural rubber (STR 5L) and cassava starch. The melt theological behavior in terms of Mooney viscosity, appare nt shear stress, and shear viscosity at 100 degreesC were quantified. We fo und that the pure MNR gave the lower apparent shear stress, sheer viscosity than did those of the blends with cassava starch. The theological data of the MNR blends increased with increasing quantity of cassava starch. The hi ghest value was observed for the blend of MNR. The rheological value was as follows: MNR > STR 5L with MNR (as the compatibilizer) > STR 5L compounds. Furthermore, theological properties increased with increasing the levels o f compatibilizer (MNR). The theological results were described in terms of intermolecular interaction between the polar groups in the natural rubber a nd cassava starch molecules. Each rubber blend was compounded, and their cu ring characteristics were studied. The pure MNR compounds exhibited a long delayed onset of vulcanization for approximately 10 min. The retardation wa s found, because the accelerator (MBT) reacted with the anhydrides in the c ompound instead of acting as an accelerator. The retardation was not observ ed for the compound with the cassava starch. The curing curves for all MNRs were not in equilibrium at a maximum torque, while the pure STR 5L compoun d gave a curing curve with a maximum torque and a slight reversion. The cur ing curve for the compound with MNR as the compatibilizer was a combination of the curing curves of MNR and STR 5L. That is, the curve was in equilibr ium at the maximum torque and the short delayed action. (C) 2001 John Wiley L Sons.